One-A-Day Echinacea 4000mg

Echinacea is the herb people buy in April for the winter ahead. These are the questions our naturopaths ask in store, and they're usually about which one rather than whether.

A good fit if

• Catching fewer colds is your goal, which is the only claim the combined evidence points towards
• You'll start before cold season rather than at the first sneeze, as the prevention trials ran for months
• You can find a product that names its species and plant part on the label
• You have no history of hay fever, asthma, eczema or other allergies
• You're an adult or a teenager over 12, which is where every regulator draws the line

Check with us first if

• You take any medicine that's processed by the liver. E. purpurea root sped up caffeine clearance by 34 per cent and changed CYP3A enzyme activity in opposite directions in the liver and gut, so its overall effect on a particular medicine can't be predicted.
• You have an autoimmune condition. Echinacea acts on the immune system, the research flags a caution, and there's a recorded case of pemphigus vulgaris (an autoimmune skin condition) getting worse.
• You're pregnant. One study following 206 exposed women, 112 in the first trimester, found no increase in major birth defects. That's reassuring, but it isn't an all-clear.
• You're breastfeeding. There's little data either way, so there's no basis for a recommendation.
• You have eyelid surgery coming up. It's best avoided because of the risk of dry eye.
• Your cold symptoms have already lasted more than 10 days, or they're getting worse rather than better.
• You take prescription medicines. Check with your doctor, pharmacist or our naturopaths before you start.

• E. purpurea fresh aerial parts, ethanolic extract. Best known for: The only echinacea any major regulator rates as well-established use rather than traditional use. Absorption: Alkamides reach measurable levels in the blood after you take it by mouth. Typical use: The evidence for prevention leans heavily on one manufacturer's fresh-plant extract of 95 per cent herb and 5 per cent root, including a 755-person, four-month placebo-controlled trial.
• E. purpurea pressed juice of fresh aerial parts. Best known for: Juice pressed from the plant rather than an alcohol extract, so it has fewer of the fat-soluble alkamides. Absorption: Not established. Typical use: A 2,458-person meta-analysis found alcohol extracts appeared to work better than pressed juices.
• E. purpurea root. Best known for: Root rather than the parts above ground, rich in alkamides and typically containing cichoric acid. Absorption: 1,600 mg a day had a measurable effect through the body, so it is absorbed and active. Typical use: The EMA rates it as traditional use only, noting there isn't enough clinical trial evidence but calling it plausibly effective.
• E. angustifolia root. Best known for: The species of Native American and Eclectic herbal tradition, and root only. Absorption: Three extraction methods were compared directly: supercritical CO2, 60 per cent ethanol and 20 per cent ethanol. Typical use: The clearest negative trial in the family used this material: none of the three extracts affected rhinovirus (common cold) infection or the illness that followed.
• E. pallida root. Best known for: Allowed in Australia, and the least studied of the three species. Absorption: Not established. Typical use: None of the trials we hold used it. That means there's no supported use to report, which is different from a use that failed.
• Liquid tonics and tinctures. Best known for: Alcohol extraction, closest to the extracts that performed best, and easy to adjust the dose. Absorption: Alkamides are absorbed by mouth. Typical use: The best-supported format, but only if the species and plant part inside are the right ones.
• Capsules and tablets. Best known for: Usually dried root or extract powder, with the dose per capsule or tablet varying hugely between brands. Absorption: A trial giving the equivalent of 10.2 g then 5.1 g of dried root a day confirmed it reached the body, and still found it didn't work. Typical use: It depends entirely on what's inside. The format tells you nothing.
• Tea. Best known for: Dried plant infused in water. Absorption: Water draws out polysaccharides and caffeic acid compounds well, but the fat-soluble alkamides poorly. Typical use: The weakest evidence of any format in the family. None of the trials we hold used a tea.

Reference values. There isn't one, and there can't be. Echinacea is a herb, not a nutrient, so there's no recommended intake, no deficiency and no food sources. Any recommended daily intake idea simply doesn't apply.

Typical supplemental range. This is the weakest link, so it's worth saying plainly: there's no common unit across capsules, tonics and teas, so trial doses and shelf doses often can't be compared at all. The strongest treatment trial used the equivalent of 10.2 g of dried root in the first 24 hours, then 5.1 g a day for four days. A study of how it's absorbed used E. purpurea root at 400 mg four times a day. The two large prevention trials used a branded fresh-plant extract whose daily dose isn't given in the published summaries. Don't assume a product on the shelf matches a trial dose without checking its label against that trial.

Upper level. No daily cap on Australia's permitted ingredients list (Schedule 1) applies to any of the three species, and no upper limit has been set. That doesn't mean anything goes. A company still has to hold evidence for the dose it uses, and European guidance limits these medicines to adults and teenagers over 12, and to short courses.

Worth knowing. How long you take it matters more than the dose. European guidance is to get advice if cold symptoms last longer than 10 days or get worse, and for use on the skin beyond a week. The longest controlled prevention course we found ran for four months, with side effect rates similar to placebo (293 compared with 306). That's the best evidence available that a season-long course is well tolerated. What you need depends on your age, diet and health, so talk to one of our naturopaths.

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Allergy to plants in the daisy (Asteraceae) family, such as ragweed, chrysanthemum, marigold and daisy. Don't take it at all.
• Allergy-prone people (atopy), with hay fever, asthma, eczema or existing allergies. Anaphylaxis has been documented in Australia, and 19 per cent of surveyed atopic patients had antibodies (IgE) that react to echinacea.
• If you take immunosuppressant medicines. Echinacea may work against their effect.
• Chemotherapy, especially etoposide. It may reduce how well cancer medicines work, and there's a case report of low platelets (thrombocytopenia).
• Autoimmune conditions. It's a herb that acts on the immune system, in a condition where the immune system is already overactive, and a flare-up has been reported.
• Medicines broken down by CYP1A2 or CYP3A. Caffeine clearance rose 34 per cent, and CYP3A activity shifted in opposite directions at two sites in the body.
• Children under 12. It didn't help, it caused significantly more rash, and the European monograph excludes them.
• Pregnancy. One prospective study found no increase in major birth defects; that isn't a guarantee it's safe.
• Breastfeeding. There's little data either way.
• Eyelid surgery. Avoid it beforehand because of the risk of dry eye syndrome.
• Cold symptoms that last more than 10 days, or get worse. Get advice rather than keep taking it.
• Rare case reports include dermatitis, anaphylaxis, thrombotic thrombocytopenic purpura, leukopenia, acute hepatitis and acute liver failure in a 2-year-old. It isn't proven echinacea caused them, but they're why the age and duration limits are real.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.